Boron neutron capture therapy kills cancer

COLUMBIA, Mo. – Cancer terminates 500,000 lives per year in the United States. The scientific crusade against cancer recently achieved a victory. A team led by Professor M. Frederick Hawthorne (University of Missouri) has developed a new form of radiation therapy that puts cancer into remission in mice. This treatment produced none of the harmful side-effects of conventional chemo and radiation cancer therapies. Clinical trials in humans could begin soon after Hawthorne secures funding.

“Since the 1930s, scientists have sought success with a cancer treatment known as boron neutron capture therapy (BNCT),” said Hawthorne, a recent winner of the National Medal of Science awarded by President Obama in the White House. “Our team at MU’s International Institute of Nano and Molecular Medicine finally found the way to make BNCT work by taking advantage of a cancer cell’s biology with nanochemistry.”

Cancer cells grow faster than normal cells and in the process absorb more materials than normal cells. Hawthorne’s team took advantage of that fact by getting cancer cells to take in and store a boron chemical designed by Hawthorne. Neutrons are subatomic particle discovered by Ernest Rutherford and Dmitri Ivanenko. In the Hawthorne experiments boron was delivered to the cells in form of 10B-enriched polyhedral borane. The delivery to the cells was achieved using unilamellar liposomes with a mean diameter of 134 nm or less, composed of an equimolar mixture of cholesterol and 1,2-distearoyl-sn-glycero-3-phosphocholine and incorporating Na3[1-(2′-B10H9)-2-NH3B10H8] in the aqueous interior and K[nido-7-CH3(CH2)15-7,8-C2B9H11] in the bilayer, were injected into the tail veins of female BALB/c mice bearing right flank EMT6 tumors.

When those boron-infused cancer cells were exposed to neutrons, the boron atom shattered and selectively tore apart the cancer cells, sparing neighboring healthy cells. The physical properties of boron-10 isotope made Hawthorne’s technique possible. This particular isotope of boron will split when it captures a neutron and release lithium and helium. The helium and lithium atoms, having high kinetic energies, collide with the cancer cell and destroy it from within, without harming the surrounding tissues. In these experiments tumor-bearing mice were irradiated for 30 min with thermal neutrons, resulting in a total fluence of 1.6 × 10^12 neutrons per cm^2. The irradiation was done 54 h after the injection of liposomes with boron.

The result was a significant suppression of tumor growth rate: Only 424% increase in tumor volume at 14 d post irradiation vs. 1551% in untreated controls. Researches also found that the suppression of the rate is even more significant if the numbers of neutrons are larger.

“A wide variety of cancers can be attacked with our BNCT technique,” Hawthorne said. “The technique worked excellently in mice. We are ready to move on to trials in larger animals, then people. However, before we can start treating humans, we will need to build suitable equipment and facilities. When it is built, MU will have the first radiation therapy of this kind in the world.”

Hawthorne believes that his discovery was possible only at the University of Missouri because MU has three features that separate it from other universities in the nation, the reason Hawthorne came to MU from the University of California, Los Angeles in 2006.

“First, it is an example of a small number of universities in the United States with a large number of science and engineering disciplines on the same campus,” said Hawthorne. “Second, the largest university research nuclear reactor is located at MU. Finally, it has strong, collegial biomedicine departments. This combination is unique.”

The Proceedings of the National Academy of Science (PNAS) recently published the study, entitled “Boron neutron capture therapy demonstrated in mice bearing EMT 6 tumors following selective delivery of boron by rationally designed liposomes.” http://www.pnas.org/content/early/2013/03/27/1303437110